Mechanical APDL Basic Analysis Guide

• If you specify stepped loads, the program handles all loads (constraints, forces, surface loads, body
  loads, and inertia loads) in the same manner. They are step-applied, step-changed, or step-removed,
  as the case may be.


• If you specify ramped loads, then:
  
  
  • All loads applied in the first load step, except film coefficients, are ramped (either from zero or
    from the value specified via BFUNIF or its GUI equivalent, depending on the type of load; see
    Table 2.12: Handling of Ramped Loads (KBC = 0) Under Different Conditions (p. 59)). Film coefficients
    are step-applied.
  
  
  
  

Note

The concept of stepped versus ramped loading does not apply to temperature-de-

pendent film coefficients (input as -N on a convection command). These are always

applied at the value dictated by their temperature function.

• All loads changed in later load steps are ramped from their previous values. If a film coefficient is
  specified using the temperature-dependent format (input as -N) for one load step and then changed
  to a constant value for the next step, the new constant value is step-applied. Note that in a full
  harmonic analysis (ANTYPE,HARM with HROPT,FULL), surface and body loads ramp as they do in
  the first load step and not from their previous values.


• For tabular boundary conditions, loads are never ramped but rather evaluated at the current time.
  If a load is specified using the tabular format for one load step and then changed to a non-tabular
  for the next, the load is treated as a newly introduced load and ramped from zero or from BFUNIF
  and not from the previous tabular value.


• All loads newly introduced in later load steps are ramped (either from zero or from BFUNIF, de-
  pending on the type of load; see Table 2.12: Handling of Ramped Loads (KBC = 0) Under Different
  Conditions (p. 59)).


• All loads deleted in later load steps are step-removed, except body loads and inertia loads. Body
  loads are ramped to BFUNIF. Inertia loads, which you can delete only by setting them to zero, are
  ramped to zero.


• Loads should not be deleted and respecified in the same load step. Ramping may not work the
  way the user intended in this case.

Table 2.12: Handling of Ramped Loads (KBC = 0) Under Different Conditions

Load Type Applied in Load Step 1 Introduced in Later Load Steps

DOF Constraints

Temperatures Ramped from TUNIF[ 2 ] Ramped from TUNIF[ 3 ]

Others Ramped from zero Ramped from zero

Forces Ramped from zero Ramped from zero

Surface

TBULK Ramped from TUNIF[ 2 ] Ramped from TUNIF

HCOEF Stepped Ramped from zero[ 4 ]

Others Ramped from zero Ramped from zero

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Specifying Load Step Options